Cable grounding in cable tray

Cable trays can be used to safely ground electrical systems, either by using the tray itself as a grounding conductor or by attaching a dedicated grounding cable.

Grounding Principles

All metallic cable trays must be grounded according to NEC Article 250. 96, regardless of whether the tray is used as an equipment grounding conductor (EGC) or not. Grounding ensures that any stray electrical currents are safely directed to the earth, reducing the risk of electric shock, equipment damage, or fire.

The grounding path must be permanent, electrically continuous, and have low impedance to allow protective devices to operate effectively under fault conditions.

Methods of Grounding

Using the Cable Tray as the Grounding Conductor Metal trays that meet conductivity and strength requirements can serve as the EGC. The tray must be electrically continuous, and bonding between tray sections is recommended using grounding clamps or bolted connections. Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 A, and aluminum trays should not be used above 2000 A.

Dedicated Grounding Cable A separate grounding conductor can be run along the tray, bonded to each or alternate tray sections with clamps. This method is preferred when using aluminum trays to prevent electrolytic corrosion or when additional safety is desired. The grounding wire should be insulated except at bonding points, where tin- or zinc-plated connectors are recommended.

Full-

Length Conductor or Sectional Connections Continuous grounding conductors provide a reliable path for fault currents. Alternatively, grounding wires can be connected at each tray joint using bolts or welds to maintain electrical continuity.

Material Considerations

Copper Wire: Excellent conductivity and corrosion resistance, ideal for most installations.

Hot-

Dip Galvanized Steel: Durable and corrosion-resistant, suitable for industrial environments. Stainless Steel: Recommended for harsh or corrosive environments. Bare copper should not be used in aluminum trays in moist environments due to corrosion risk.

Safety and Compliance

Ensure grounding resistance is low (ideally ≤4 ohms) to maintain system effectiveness. Keep grounding conductors clear of flammable or corrosive materials.

Follow NE

C standards for tray fill, separation of power and data cables, and bonding requirements. Use approved tray-rated cables to maintain safety and code compliance. By following these practices, cable trays can provide a safe, reliable grounding path, protecting both personnel and equipment while ensuring compliance with electrical codes.